The Effects of THC and Nicotine on Attention: A Narrative Review.

Since cannabis and nicotine are two of most commonly used substances and are often used together, this paper will review the effects of cannabis (specifically THC, or tetrahydrocannabinol) and nicotine on selective attention, sustained attention, visuospatial attention, attentional bias, and attentional disorders. This review includes preclinical and clinical findings throughout all periods of development and adulthood. Selective attention is directly impacted by cannabis use, while reaction time is dependent on the timing of the last cannabis exposure. Among individuals who use cannabis, there is an attentional bias that reduces anxiety and increases focus on cannabis-related cues. Preclinical studies show that cannabis induces attention deficits that persist even after an abstinence period. Preclinical and clinical studies of prenatal cannabis exposure (PCE) provide evidence that offspring will have an increased risk for drug-seeking behavior, attention deficits, and impulsivity, which may lead to attentional disorders such as attention deficit hyperactivity disorder (ADHD) and schizophrenia. Nicotine has a dose-dependent effect on attention in adults, though preclinical studies have shown mixed results, possibly due to differences in experimental design. Prenatal nicotine exposure (PNE) impairs attentional networks by increasing one's risk for ADHD, oppositional defiant disorder, and conduct disorder. Additionally, maternal secondhand smoke exposure is linked to ADHD/conduct disorder risk in offspring. Preclinical studies on prenatal nicotine exposure suggest that there may be sex differences in which males are affected more so than females with PNE. Summary: Overall, cannabis/THC impairs attention, and nicotine enhances attention; however, both substances impair attention when individuals are exposed prenatally.